Thought Experiment When empiricism is out of reach, run a disciplined counterfactual: one isolated change, fixed conditions, step-by-step mechanism, and a hard bound on implications. When to Use - You need behavior under failure, scale, or policy you cannot cheaply trigger or measure (region outage, 100x load, one-way architecture). - A decision is expensive or irreversible and a mental trace can surface break points before commit. - Edge cases are too costly to stage, but a mechanistic chain can still expose missing controls. When NOT to Use - A cheap real test exists (load test, flag, query…